1. Field of the Invention
This invention relates to control valves and, more particularly, to control valves which control the height of vehicles and the like.
2. Description of the Prior Art
One of the great advantages of air spring suspensions for motor vehicles is the fact that the air springs can be easily adjusted by the introduction of more air or by the exhaustion of some air from the spring to control the height of the vehicle frame and body with respect to the axle and the character of the ride of the vehicle. The adjustability of the air spring is particularly useful on vehicles like pick-up trucks where the load carried by the vehicle may vary greatly. In order to automatically control the height of the vehicle, air control valves have been operably connected to the air spring and an air compressor.
The control valve detects the level of the frame with respect to the axle. If the frame is too low, the control valve will allow the air compressor to supply air to the air spring to raise the frame. If the frame is too high the control valve will allow air within the air spring to escape. One such control valve is disclosed in U.S. Pat. No. 2,989,983 issued to Valentine on June 27, 1961. The Valentine patent discloses a control valve with a supply port entering into a first chamber. A disc is mounted at the bottom of the first chamber. Below the disc is a bore with a piston slidable mounted therein. The piston has a passage therethrough leading from the top end to the bottom end thereof. The bore also has a side passage leading to the air spring. When the frame is too high, the piston is lowered away from the disc allowing the passage to be in fluid connection with the bore. Air leaks into the passage through the piston to alleviate the excess air pressure within the air spring. When the frame is too low, the piston lifts the disc up allowing air from the air port to communicate with the passage to the air spring.
Another such control valve is disclosed in U.S. Pat. No. 4,064,910 issued to Weisenberger on Dec. 27, 1977. In the Weisenberger patent, instead of a disc, a conical valve closure member closes an end of a passage through the piston stem and also abuts the shoulders leading to the bore which houses the stem. The manner of operation is the same as that for the device described in the Valentine patent.